Over-the-road trailers in common use today carry substantial loads weighing tens of thousands of pounds. To support these heavy loads, many of the trailers are mounted on multiple or tandem axles. Due to unlimited configurations in which various loads can be distributed within a trailer, unbalanced and improper loading can readily occur. In order to adjust and compensate for the different loading distributions, the undercarriage of such trailers is designed whereby the body portion of the trailer can be shifted relative to the position of the tandem axles thereunder. In other words, the spacing of the axles can be shifted forwardly or rearwardly to alter the distribution of weight among the front tandem axle, the rear tandem axle and the load bearing downwardly on a tongue or fifth wheel.
In order to perform the aforementioned repositioning of the trailer body relative to the tandem axles, a pair of rails in combination with sliding components are longitudinally disposed on the underside of the trailer body and above the tandem axles. A carriage containing the tandem axles is adapted to slide along such rails.
To lock the carriage at a particular location therealong, a series of uniformly spaced, transverse bores are cooperatively spaced along the two rails. Two pairs of pegs, one pair toward the front of the tandem axle carriage and the other pair toward the rear of the tandem axle carriage, provide locking means to retain the carriage at the desired relative location. The diameter of each of the pins is less than the diameter of the transverse bores. The pins are all interconnected by a linkage such that all four of the pins are simultaneously either seated in the respective bores in a locking position, or withdrawn from the bores in an extracted position. The pins are spring-loaded whereby the pins automatically attempt to seat themselves in such locked position.
A release handle is connected to the linkage which, when pulled, simultaneously extracts all four pins whereby the carriage can be repositioned and the pins allowed to seek appropriate bores to securely establish the new location of the trailer body relative to the tandem axles.
The difficulty with the aforedescribed arrangement lies with the fact that the magnitude of the masses involved with the trailer body and the tandem axles and the forces therebetween tends to cause the pins to be jammed in the locking position. Thus, when an operator attempts to extract the pins by pulling the release handle, the operator is incapable of applying sufficient force to extract the lodged pins.
Two approaches are commonly utilized to accomplish extraction of the lodged pins. In the first approach, the operator uses a tractor unit attached to the trailer to rock the trailer back and forth in an attempt to locate a position whereby the pins are no longer lodged and the release handle can be pulled. Sometimes several such rocking maneuvers must be conducted before the right combination is randomly discovered whereby the operator, working alone, can accomplish such repositioning. In most cases, however, such a procedure is time consuming and very frustrating to the operator.
In the other approach, the operator employs the services of an assistant. Under these circumstances, the operator rocks the trailer with the tractor unit while the assistant pulls on the release handle. Since the assistant can apply a steady pressure, the pins can be extracted more quickly than with the one-person approach. However, the use of the assistant introduces another concern of major importance. While pulling on the release handle, the assistant must unavoidably be situated near the release handle in order to apply the necessary force. Since the release handle is located in close proximity to the tandem axles, the assistant must be situated undesirably close to the wheels of the axles while the operator is causing the trailer to be rocked back and forth. Such an arrangement obviously subjects the assistant to uncertain danger and substantial risk.
Some prior art has been developed which allows the assistant to be somewhat more removed from the immediate proximity of the axles but, nevertheless, requires the services of an assistant, who may not always be available.
Other prior art has been developed which can provide a constant bias on the release lever while the operator is rocking the trailer, thus eliminating the dangerous exposure to the assistant. Unfortunately, such prior art requires adaptation of the undercarriage of the trailer to incorporate such apparatus therein. Thus, such apparatus becomes a permanent installation and each separate trailer requires its own separate and individual set of apparatus.
What is needed is a device which is portable so that it can realistically be used for repeated applications on numerous trailers, is adapted for a one-person application, and which is self-contained thereby avoiding the need to modify the undercarriage of existing trailers.